1. Field of the Invention
The present invention generally relates to mobile communication systems and mobile station apparatuses, and, more particularly, to a mobile communication system in which a radio zone where a mobile station is to enter a wait state is determined by the electric field intensity of a received radio wave that arrives from a radio base station, and to a mobile station apparatus that receives communication service by accessing such a mobile communication system.
The present invention also relates to a mobile communication system wherein a mobile station selects a base station to which a request for a message channel is to be issued, based on announcement information from the base station.
2. Description of the Related Art
Recently, a variety of mobile stations including an automobile mobile station and a portable mobile station access a mobile communication system. With a competition between a plurality of carriers as a background, the number of mobile stations is increasing.
A mobile communication system may have a large-zone construction in which a base station covers a relatively wide service area or a small-zone construction in which a plurality of base stations cover a service area.
In a mobile communication system, radio base stations operated on a small transmission power and forming microcells or picocells are provided at the center of a big city characterized by a particularly large volume of traffic so that a multilayer cell is formed.
Radio base stations operated on a small transmission power are also provided in an underground passage and a tunnel in order to enlarge a radio zone sufficiently to eliminate a dead zone.
FIG. 1 shows a construction of a conventional mobile communication system.
Referring to FIG. 1, radio base stations 611 and 612 form adjacent radio zones 621 and 622, respectively. In the radio zone 621, a radio base station 613 forming a microcell 63 and a radio base station 614 forming a picocell 64 are provided so as to form a multilayer. Mobile stations 651-65N are located movable in the radio zones 621 and 622, the microcell 63 and the picocell 64.
In the radio base station 611, an antenna 661 is connected to an antenna terminal of a transmission and reception unit 681 via a common antenna equipment unit 671. A control terminal of the transmission and reception unit 681 is connected to an input and output terminal of a base station control device 691. A line terminal provided in the transmission and reception unit 681 and a communication port of the base station control device 691 are connected to a control station (not shown) via a transmission device 701 and a communication link 711.
Since the radio base stations 612-614 have the same construction as the radio base station 611, the corresponding elements are designated by using suffixes 2-4 in the description below, and the illustration and description thereof are omitted.
An antenna 721 of the mobile station 651, is connected to an antenna terminal of a transmission and reception unit 741 via a common antenna equipment unit 731. A modulated input and a demodulated output of the transmission and reception unit 741 are connected to a microphone 751 and a speaker 761, respectively. A control terminal of the transmission and reception unit 741 is connected to a control terminal of a control unit 771. An input and output terminal of the control unit 771 is connected to a display and operation unit 781.
Since the construction of the mobile stations 652-651 is the same as the mobile station 651, the corresponding elements are designated by using suffixes 2xe2x88x92N in the description below, and the illustration and description thereof are omitted.
The base station control device 691 of the radio base station 611 in the above-described mobile communication system is directed by a center (not shown) via the communication link 711 and the transmission device 701 to generate announcement information including a wait enabled level and a wait disabled level as shown in FIG. 2 and transmits the announcement information to a predetermined control radio channel (hereinafter, simply referred to as a control channel) via the transmission and reception unit 681, the antenna common equipment unit 671 and the antenna 661.
In addition to the wait enabled level and the wait disabled level, the announcement information also includes a message type identifying transmitted information as the announcement information, a mobile station transmission power specification specifying a transmission power of the mobile station, a location code indicating a location of the radio zone (service area), and the like. However, the information items other than the wait enabled level and the wait disabled level does not have to do with the present invention, and the description thereof is omitted.
The control unit 771 of the mobile station 651 maintains a control channel table listing all the radio channels over which the announcement information described above is transmitted from the radio base stations forming the respective radio zones to which the mobile station 651 may be located. Further, upon power-on, the control unit 771 measures sequentially the electric field intensity L1 of the control channel registered in the control table channel by controlling the transmission and reception unit 741 ((1) of FIG. 3). A determination is then made as to whether or not the measured electric field intensity is greater than a predetermined threshold level Lth ((2) of FIG. 3).
The control unit 771 registers the control channels for which a determination that the measured electric field intensity is greater than the threshold level Lth is obtained, in a prescribed area (hereinafter, referred to as a candidate zone register) in a main memory. The electric field intensity of the registered control channel is also registered in the candidate zone register so that the correspondence between the control channel and the associated electric field intensity is specified ((3) of FIG. 3).
When the control unit 771 has completed a series of the above-described processes (hereinafter, referred to as a measurement process) for all the control channels registered in the control channel table, the control unit 771 determines whether or not the candidate zone register stores any control channel ((4) of FIG. 3). If an affirmative answer is given, the control unit 771 sorts the entries in the candidate zone register according to the ascending order of the electric field intensity ((5) of FIG. 3).
The control unit 771 refers to the candidate zone register when the sorting process has been completed and receives the announcement information via the individual control channels registered in the candidate zone register ((6) of FIG. 3). The control unit 771 measures the electric field intensity again ((7) of FIG. 3). Further, the control unit 771 compares the electric field intensity L2 and the wait enabled level Lth included in the announcement information ((8) of FIG. 3). When the former is lower in level than the latter, a similar comparison is conducted for the other control channels registered in the candidate zone register ((9) of FIG. 3). Hereinafter, a series of processes performed subsequent to the measurement process is referred to as a zone determination process. The control unit 771 restarts the measurement process when the electric field intensity is found to be below the wait enabled level Lth for all the control channels subjected to the comparison ((10) of FIG. 3).
If the electric intensity field of any of the control channels is found to be equal to or exceeds the wait enabled level, the control unit 771 establishes that control channel as a control channel for the radio zone in which the mobile station is to register its location, issues a call and receives an incoming call ((11) of FIG. 3). Thereafter, the control unit 771 enter a wait state ((12) of FIG. 3).
The operations relating to registering of a location, issuing of a call or receiving of an incoming call performed by the mobile station 651 and the radio base station 611 are not directly related to the present invention, and the description thereof will be omitted below.
The operation performed by the radio base stations 612-614 is the same as the above-described operation of the radio base station 611, and the description thereof is omitted. Also, the operation performed by the mobile stations 652-65N is the same as the above-described operation of the mobile station 651, and the description thereof is omitted.
In the conventional system described above, if the mobile station 651 is located inside the microcell 63 and near the border with respect to the radio zone 621, as indicated by the broken line in FIG. 4, and if the electric field intensity of the radio wave arriving from the radio base station 611 is higher than that of the radio wave received from the radio base station 613, the mobile station 651 is set up for a wait in the radio zone 621. As illustrated, the radio zone 621 is formed outside the microcell 63 in which the mobile station 651 is actually located.
In such a case, the microcell 63 and the picocell 64 provided with the aim of handling a large volume of traffic are not accessed by the mobile station 651. The traffic otherwise handled by the microcell 63 is imposed as a load on the radio base station 611, thus causing the operating efficiency and the service quality to be dropped.
When the propagation loss of the radio wave that arrives at the mobile station 651 from the radio base station 611 increases due to the propagation characteristic of the radio transmission channel varying depending on the speed of the mobile station mobile station 651 and the path of the movement, the mobile station 651 may leave a zone when it is not necessary and performs the measurement process. Even when a call originated in the mobile station 651 becomes a successful call so that a conversation is established without the mobile station 651 leaving the zone, the speech quality may be dropped if there is a large propagation loss, with the result that switching of message channels occur too frequently during the conversation.
Given that the microcell 63 or the picocell 64 is provided in order to serve the dead area located inside the radio zone 621, the mobile station 651 may be set up for a wait in a radio zone located outside the cell (the microcell 63 or the picocell 64) in which the mobile station 651 is actually located. In this case, the microcell 63 or the picocell 64 remain unused so that the dead area is not efficiently served, a first aspect of the problem with the conventional mobile communication system.
A description will now be given, with reference to FIG. 5, of the flow of call origination operation in the conventional mobile communication system, in order to explain a second aspect of the problem with the conventional mobile communication system. In the following explanation of the second aspect, the PDC mobile communication system employed primarily in Japan is assumed.
In the conventional mobile communication system, when the user of a mobile station turns the power on (ST701), the mobile station measures a reception level of a perch channel provided for a base station (ST702). A perch channel is a term used in the PDC mobile communication system to refer to a channel provided for each of the base stations to allow a mobile station to determine a reception level with respect to the base station. In the PDC system, a perch channel is mainly used to transmit announcement information from the base station to the mobile station. The claims refer to a perch channel as a reception-level determining channel. If it is determined that the reception level exceeds a predetermined level (YES in ST703), the mobile station sorts the perch channels according to the ascending order of reception levels and stores the perch channels and the associated reception levels in a memory provided in the mobile station (ST704). A determination is then made as to whether the reception levels in all the perch channels have been measured (ST705).
If no perch channels and associated reception levels are stored in the memory (NO in S706), the mobile station displays an out-of-the-zone message in a display device (S707). When perch channels and associated reception levels are stored in the memory (YES in S706), the mobile station measures the reception level in the perch channel having the highest reception level according to the memory. If it is determined that the measured reception level exceeds a wait enabled level contained in the announcement information from the base station, the mobile stations is set up for a wait in the base station providing the highest reception level (S708).
The mobile station in a wait state sends a call request to the base station in which it is set up for a wait (S709). The mobile station notifies the base station of the perch channel codes and the reception levels provided by the base stations other than the notified base station.
If the level of reception from the mobile station issuing the request exceeds a predetermined level that enables assigning of a message channel (YES in S710), and if there is an unused message channel (YES in S711), the base station receiving the request from the mobile station assigns a message channel to the requesting mobile station (S712). If the level of reception from the mobile station is below the predetermined level (NO in S710), or if there is no unused message channel (NO in S711), the base station receiving the request refers to the reception levels of the adjacent base stations reported by the mobile station and designates one of the adjacent base stations as a base station for the requesting mobile station (S713).
The mobile station that receives, from the base station, a signal for assigning a message channel can use the assigned message channel to establish a call connection with the corresponding base station (S714).
Thus, the mobile station located at a point where there is an overlap of a plurality of zones formed by respective base stations is set up for a wait in the base station whose perch channel provides the highest reception level. When originating or receiving a call, the mobile station issues a request for a message channel to the base station in which the mobile station is set up for a wait.
However, it is not always best for the mobile station in the mobile communication system to issue a request for a message channel to the base station providing the highest reception level in the perch channel.
A relatively large service area formed, for example, by the base station A as shown in FIG. 31 is assumed. This large-zone construction formed by the base station A may include an area characterized by a concentrated traffic, resulting in a shortage of message channels in that area. In order to remedy this shortage, the base station B having a smaller transmission power and capable of forming a smaller-zone construction than the base station A is provided within the service area formed by the base station A. Provision of the base station B would serve the intended purpose if a mobile station within the zone formed by the base station B requests a message channel from the base station B.
However, a problem with the conventional mobile communication system is that the mobile station requests a message channel from the base station A providing a higher reception level than the base station B instead of requesting it from the base station B provided to handle an increased local traffic, with the result that the base station B remains unused to handle call originating or call incoming in the mobile station.
Accordingly, a general object of the present invention is to provide a mobile communication system and a mobile station apparatus in which the aforementioned problems of the conventional system are eliminated.
Another and more specific object of the present invention is to provide a mobile communication system and a mobile station apparatus in which a radio base station adapts itself to a dynamically established traffic distribution, or in which a mobile station can most successfully enter a radio zone in which it is actually located so as to be set up for a wait therein.
Still another object of the present invention is to assign order of priority to a plurality of base stations constituting a mobile communication system so that a mobile station requests a message channel from a base station having a higher priority than others in order to start communicating via that base station.
FIG. 6 is a block diagram of a mobile communication system according to claim 1 of the present invention. The mobile communication system according to claim 1 comprises a plurality of radio base stations 11-1N forming respective radio zones and effecting a radio channel setting control in accordance with a predetermined procedure, and a mobile station 2 selecting, as a wait zone, one of the radio zones that satisfies a criteria demanded by the predetermined procedure, and receiving communication service via the selected wait zone. Each of the radio base stations 11-1N comprises a traffic control unit 3 for setting a traffic distribution for the plurality of radio zones, and an announcing unit 4 for generating announcement information including the order of priority assigned to the plurality of radio zones, the order of priority being assigned in accordance with a probability density given to each of the plurality of radio zones under the distribution set by the traffic control unit 3, and for transmitting the announcement information to the radio zone formed by the radio station to which the announcing unit 4 belongs. The mobile station 2 comprises an announcement information receiving unit 5 for receiving the announcement information transmitted by the announcing unit 4 in accordance with the predetermined procedure, and a wait control unit 6 for selecting one of the radio zones as a wait zone, the radio zone to which a highest priority is assigned being a first candidate for selection by the wait control unit 6.
FIG. 7 shows a mobile communication system according to claim 2 of the present invention. The mobile communication system according to claim 2 comprises: a plurality of radio base stations 111-11N forming one or a plurality of radio zones and one or a plurality of small-scale radio zones, resulting in a hierarchy of overlapping radio zones, and effecting a radio channel setting control in accordance with a predetermined procedure; and a mobile station 12 accessing one of the radio zones formed by the respective one of the plurality of radio base stations 111-11N, in accordance with a predetermined procedure, and receiving communication service via the accessed radio zone. Each of the plurality of radio base stations 111-11N comprises an announcing unit 13 for transmitting announcement information which includes identification information for identifying radio channels assigned to respective radio zones and small-scale radio zones, via the radio channel assigned to the radio zone formed by the radio base station to which the announcing unit 13 belongs, the identification information being arranged in the announcement information so as to correspond to the hierarchy of overlapping radio zones. The mobile station 12 comprises: an announcement information receiving unit 14a for receiving the announcement information transmitted by the announcing unit 13a, in accordance with the procedure for radio channel setting control; a measuring unit 15a for measuring an electric field intensity for the radio channel corresponding to the identification information included in the announcement information received by the announcement information receiving unit 14a; and a wait control unit 16a for comparing an electric field intensity measured by the measuring unit 15a with a preset threshold level, and designating a radio zone to which the radio channel lowest in the hierarchy is assigned as a wait zone in which to receive the communication service, on the condition that the electric field intensity measured by the measuring unit 15a exceeds the preset threshold level.
The mobile communication system according to claim 3 comprises: a plurality of radio base stations 111-11N forming one or a plurality of radio zones and one or a plurality of small-scale radio zones, resulting in a hierarchy of overlapping zones, and effecting a radio channel setting control in accordance with a predetermined procedure; and a mobile station 12 accessing one of the radio zones formed by the respective one of the plurality of radio base stations 111-11N in accordance with a predetermined procedure, and receiving communication service via the accessed radio zone. Each of the plurality of radio base stations 111-11N comprises an announcing unit 13a for transmitting announcement information which includes identification information for identifying the one or the plurality of radio zones and the one or the plurality of small-scale radio zones, via the radio channel assigned to the radio zone formed by the radio base station to which the announcing unit 13a belongs, the identification information being arranged in the announcement information according to respective positions in the hierarchy of overlapping zones. The mobile station 12 comprises: an announcement information receiving unit 14a for receiving the announcement information transmitted by the announcing unit 13a, in accordance with the procedure for radio channel setting control; a measuring unit 15a for measuring an electric field intensity for the radio zone corresponding to the identification information included in the announcement information received by the announcement information receiving unit 14a; and a wait control unit 16a for comparing an electric field intensity measured by the measuring unit 15a with a preset threshold level, and designating, as a wait zone in which to receive the communication service, a radio zone lowest in the hierarchy of overlapping zones on the condition that the electric field intensity measured by the measuring unit 15a exceeds the threshold level.
The mobile communication system according to claim 4 comprises: a plurality of radio base stations 111-11N forming one or a plurality of radio zones and one or a plurality of small-scale radio zones, resulting in a hierarchy of overlapping zones, and effecting a radio channel setting control in accordance with a predetermined procedure; and a mobile station 12 accessing one of the radio zones formed by the respective one of the plurality of radio base stations 111-11N in accordance with a predetermined procedure, and receiving communication service via the accessed radio zone. Each of the plurality of radio base stations 111-11N comprises an announcing unit 13b for transmitting announcement information which includes identification information for identifying radio channels for the one or the plurality of radio zones and the one or the plurality of small-scale radio zones, via the radio channel assigned to the radio zone formed by the radio base station to which the announcing unit 13b belongs, the identification information being arranged in the announcement information according to respective positions in the hierarchy of overlapping zones. The mobile station 12 comprises: an announcement information receiving unit 14b for receiving the announcement information transmitted by the announcing unit 13b, in accordance with the procedure for radio channel setting control; a measuring unit 15b for measuring an electric field intensity for the radio channel corresponding to the identification information included in the announcement information received by the announcement information receiving unit 14b; and a wait control unit 16b for comparing an electric field intensity measured by the measuring unit 15b with a preset threshold level, and designating one of the radio channels, which is assigned to the radio zone lowest in the hierarchy and for which the control unit 16b has determined that the electric field intensity measured by the measuring unit 15b exceeds the preset threshold level, as a radio channel via which to receive the communication service.
The mobile communication system according to claim 5 comprises: a plurality of radio base stations 111-11N forming one or a plurality of radio zones and one or a plurality of small-scale radio zones, resulting in a hierarchy of overlapping zones, and effecting a radio channel setting control in accordance with a predetermined procedure; and a mobile station 12 accessing one of the radio zones formed by the respective one of the plurality of radio base stations 111-11N, in accordance with a predetermined procedure, and receiving communication service via the accessed radio zone. Each of the plurality of radio base stations 111-11N comprises an announcing unit 13c for transmitting announcement information which includes identification information for identifying the one or the plurality of radio zones and the one or the plurality of small-scale radio zones, via the radio channel assigned to the radio zone formed by the radio base station to which the announcing unit 13c belongs, the identification information being arranged in the announcement information according to respective positions in the hierarchy of overlapping zones. The mobile station 12 comprises: an announcement information receiving unit 14c for receiving the announcement information transmitted by the announcing unit 13c, in accordance with the procedure for radio channel setting control; a measuring unit 15c for measuring an electric field intensity for the radio zone corresponding to the identification information included in the announcement information received by the announcement information receiving unit 14c; and a wait control unit 16c for comparing an electric field intensity measured by the measuring unit 15c with a preset threshold level, and designating, as a wait zone in which to receive the communication service, a radio zone identified by the identification information to be lowest in the hierarchy of overlapping zones, on the condition that the electric field intensity measured by the measuring unit 15a exceeds the threshold level.
The mobile communication system according to claim 6 comprises: a plurality of radio base stations 111-11N forming one or a plurality of radio zones and one or a plurality of small-scale radio zones, resulting in a hierarchy of overlapping zones, and effecting a radio channel setting control in accordance with a predetermined procedure; and a mobile station 12 accessing one of the radio zones formed by the respective one of the plurality of radio base stations 111-11N, in accordance with a predetermined procedure, and receiving communication service via the accessed radio zone. Each of the plurality of radio base stations 111-11N comprises an announcing unit 13d for transmitting announcement information which includes first identification information for identifying a radio channel assigned to the radio zone formed by the radio base station to which the announcing unit 13d belongs, as well as including second identification information identifying the radio zones and the small-scale radio zones which overlap the radio zone formed by the radio base station to which the announcing unit 13d belongs, via the radio channel assigned to the radio zone formed by the radio base station to which the announcing unit 13d belongs, the second identification information being arranged in the announcement information according to respective positions in the hierarchy of overlapping zones. The mobile station 12 comprises: an announcement information receiving unit 14d for receiving the announcement information transmitted by the announcing unit 13d, in accordance with the procedure for radio channel setting control; a measuring unit 15d for measuring an electric field intensity for the radio channel corresponding to the identification information included in the announcement information received by the announcement information receiving unit 14d; and a wait control unit 16d for comparing an electric field intensity measured by the measuring unit 15d with a preset threshold level, determining the radio channel which is identified by the associated second identification information, if available, to have a lowest hierarchical order, and designating, as a wait zone in which to receive the communication service, the radio zone to which the determined radio channel is assigned, on the condition that the electric field intensity measured by the measuring unit 15d exceeds the threshold level.
The mobile communication system according to claim 7 comprises: a plurality of radio base stations 111-11N forming one or a plurality of radio zones and one or a plurality of small-scale radio zones, resulting in a hierarchy of overlapping zones, and effecting a radio channel setting control in accordance with a predetermined procedure; and a mobile station 12 accessing one of the radio zones formed by the respective one of the plurality of radio base stations 111-11N in accordance with a predetermined procedure, and receiving communication service via the accessed radio zone. Each of the plurality of radio base stations 111-11N comprises an announcing unit 13e for transmitting announcement information which includes first identification information for identifying a radio channel assigned to a radio zone formed by the radio base station to which the announcing unit 13e belongs, as well as including second identification information identifying the radio zones and the small-scale radio zones which overlap the radio zone formed by the radio base station to which the announcing unit 13e belongs, over the radio zone formed by the radio base station to which the announcing unit 13e belongs, the second identification information being arranged in the announcement information according to respective positions in the hierarchy of overlapping zones. The mobile station 12 comprises: an announcement information receiving unit 14e for receiving the announcement information transmitted by the announcing nit 13e, in accordance with the procedure for radio channel setting control; a measuring unit 15e for measuring an electric field intensity for the radio zone corresponding to the identification information included in the announcement information received by the announcement information receiving unit 14e; and a wait control unit 16e for comparing an electric field intensity measured by the measuring unit 15e with a preset threshold level, determining the radio zone corresponding to the radio channel which is identified by the associated second identification information, if available, to have a lowest hierarchical order, and designating the determined radio zone as a wait zone in which to receive the communication service on the condition that the electric field intensity measured by the measuring unit 15e exceeds the threshold level.
The mobile communication system according to claim 8 comprises: a plurality of radio base stations 111-11N forming one or a plurality of radio zones and one or a plurality of small-scale radio zones, resulting in a hierarchy of overlapping zones, and effecting a radio channel setting control in accordance with a predetermined procedure; and a mobile station 12 accessing one of the radio zones formed by the respective one of the plurality of radio base stations 111-11N, in accordance with a predetermined procedure, and receiving communication service via the accessed radio zone. Each of the plurality of radio base stations 111-11N comprises an announcing unit 13f for transmitting announcement information which includes a hierarchical (equal or subordinate) order of the radio zone formed by the radio base station to which the announcing unit 13f belongs with respect to the overlapping radio zones and small-scale radio zones, and which also includes identification information for identifying radio channels assigned to the radio zone formed by the radio base station to which the announcing unit 13f belongs and the overlapping radio zones and small-scale radio zones, via the radio channel assigned to the radio zone formed by the radio base station to which the announcing unit 13f belongs. The mobile station 12 comprises: an announcement information receiving unit 14f for receiving the announcement information transmitted by the announcing unit 13f, in accordance with the procedure for radio channel setting control, for extracting the identification information from the announcement information, and for determining the hierarchy of the radio zones to which the radio channels identified by the identification information are assigned; a measuring unit 15f for measuring an electric field intensity for the radio channel corresponding to the identification information obtained by the announcement information receiving unit 14f; and a wait control unit 16f for comparing an electric field intensity measured by the measuring unit 15f with a preset threshold level, and designating a radio zone to which the radio channel lowest in the hierarchy is assigned as a wait zone in which to receive the communication service, on the condition that the electric field intensity measured by the measuring unit 15f for the radio channel lowest in the hierarchy exceeds the preset threshold level.
The mobile communication system according to claim 9 comprises: a plurality of radio base stations 111-11N forming one or a plurality of radio zones and one or a plurality of small-scale radio zones, resulting in a hierarchy of overlapping zones, and effecting a radio channel setting control in accordance with a predetermined procedure; and a mobile station 12 accessing one of the radio zones formed by the respective one of the plurality of radio base stations 111-11N, in accordance with a predetermined procedure, and receiving communication service via the accessed radio zone. Each of the plurality of radio base stations 111-11N comprises an announcing unit 13g for transmitting announcement information which includes a hierarchical (equal or subordinate) order of the radio zone formed by the radio base station to which the announcing unit 13g belongs with respect to the overlapping radio zones and small-scale radio zones, and which also includes identification information for identifying the radio zone formed by the radio base station to which the announcing unit 13g belongs and the overlapping radio zones and small-scale radio zones, over the radio zone formed by the radio base station to which the announcing unit 13g belongs. The mobile station 12 comprises: an announcement information receiving unit 14g for receiving the announcement information transmitted by the announcing unit 13g, in accordance with the procedure for radio channel setting control, for extracting the identification information from the announcement information, and for determining the hierarchy of the radio zones corresponding to the identification information; a measuring unit 15g for measuring an electric field intensity for the radio zone corresponding to the identification information extracted by the announcement information receiving unit 14g; and a wait control unit 16g for comparing an electric field intensity measured by the measuring unit 15g with a preset threshold level, and designating a radio zone lowest in the hierarchy determined by the announcement information receiving unit 14g as a wait zone in which to receive the communication service, on the condition that the electric field intensity measured by the measuring unit 15g for the radio zone lowest in the hierarchy exceeds the preset threshold level.
The announcing unit of the mobile communication system according to claim 10 comprises a unit for adding, in the announcement information, preset threshold values individually provided for the radio zone formed by the radio base station to which the announcing unit belongs and the overlapping radio zones and small-scale radio zones, resulting in a hierarchy that corresponds to the hierarchy of overlapping zones. The wait control unit 16 employs the threshold values added to the announcement information by the announcing unit in making comparisons with the electric field intensity.
The announcing unit of the mobile communication system according to claim 11 comprises a unit for adding a relative value indicating the preset threshold value for the zone formed by the radio base station to which the announcing unit belongs, in the form of a difference with respect to a reference value for the threshold value. The announcement information receiving unit includes a unit for determining the relative value added to the announcement information, in relation to the radio zone in which the announcement information is received. The wait control unit compares the electric field intensity measured by the measuring unit with a sum of the reference value and the relative value determined by the announcement information receiving unit in relation to the radio zone in which the electric field intensity is measured.
The announcing unit of the mobile communication system according to claim 12 comprises a unit for adding relative values indicating the preset threshold values for the radio zone formed by the radio base station to which the announcing unit belongs and the overlapping radio zones and small-scale radio zones, in the form of differences with respect to a reference value common to the threshold values, resulting in a hierarchy that corresponds to the hierarchy of overlapping zones. The wait control unit compares the electric field intensity with a sum of the relative value and the reference value.
The mobile station 12 of the mobile communication system according to claim 13 comprises a zone determination unit 17 for performing a cyclic measurement of the electric field intensity of the radio zones in which the mobile station 12 can be located, comparing a measured electric field intensity with a lower acceptance value by which an entry into the radio zone is enabled, stopping processes of measurement and comparison when it is found that the former exceeds the latter, and selecting the associated radio zone as a candidate in which the announcement information receiving unit 14 is to receive the announcement information.
The wait control unit of the mobile communication system according to claim 14 compares the electric field intensity measured by the measuring unit with the threshold value in the descending order of the hierarchy in the radio zones subject to the measurement, and designates the radio zone for which it is found that the former exceeds the latter as a wait zone.
The measuring unit of the mobile communication system according to claim 15 comprises a unit which omits a measurement of the radio zone selected by the zone determination unit 17 and substitutes therefor the electric field intensity measured by the zone determination unit.
FIG. 8 is a block diagram showing the invention described in claim 16.
The mobile station according to claim 16 comprises an announcement information receiving unit 21 for receiving announcement information including orders of priority assigned to radio zones formed by a plurality of radio base stations, the reception by the announcement information receiving unit 21 being conducted according to a descending order of preset traffic distribution and in accordance with a radio channel setting control procedure; a wait unit 23 for determining whether the radio zone associated with the order of priority included in the announcement information received by the announcement information receiving unit 21 satisfies a criteria adapted for the radio channel setting control procedure, and for designating the radio zone for which an affirmative answer is given as a wait zone; and a communication control unit 25 which receives communication service from the radio base station forming the radio zone designated by the wait unit 23.
The mobile communication system according to claim 17 comprises: a plurality of base stations forming respective radio zones that overlap each other; a mobile station transportable between said radio zones; wherein each of said plurality of base stations comprises: announcing means for sending announcement information including an order of priority of said plurality of base stations to the mobile station located in one of said radio zones, and said mobile station comprises: control means for selecting the base station to which a request for a message channel is to be issued, based on the order of priority of the base stations included in the announcement information transmitted from said plurality of base stations.
According to this aspect of the present invention, the base station as shown in FIG. 31 in which the mobile station is set up for a wait transmits the announcement information that includes the order of priority specifying, for example, that the base station B be given the priority over the base station A in selecting a base station from which to request a message channel. Therefore, the mobile station requests a message channel from the base station B in accordance with the order of priority included in the announcement information from the base station A.
Since the mobile station requests a message channel from the base station B instead of the base station A providing a higher reception level, the base station B can be used efficiently to handle call originating and call incoming in the mobile station.
The mobile station according to claim 18 further comprises: announcement information receiving means for receiving the announcement information including the order of priority of said plurality of base stations and transmitted from said plurality of base stations; and transmission means for issuing a request for a message channel to the base station selected by said control means.
According to this aspect of the present invention, the announcement information receiving means of the mobile station receives the announcement information including the order of priority of the base stations from, for example, the base station A and the base station B as shown in FIG. 31. The transmission means of the mobile station transmits a request for a message channel from a base station selected by the control means. For example, the mobile station may send the request to the base station B having the highest priority.
The mobile station according to claim 19 further comprises: storage means for storing the announcement information; measuring means for measuring a reception level in reception-level determining channels in a descending order of priority of said plurality of base stations, based on the announcement information stored in said storage means and including the order of priority and based on information relating to the reception-level determining channels.
According to this aspect of the present invention, the memory means of the mobile station stores the announcement information received by the announcement information receiving means from, for example, the base station A and the base station B as shown in FIG. 31 and including the order of priority of the base stations. Measurement of the reception level by the measuring means starts with the base station B having the highest priority, based on the order of priority of the base stations A and B stored in the storing means and the information relating to the perch channel corresponding to the respective base stations. The measuring means notifies the control means of the reception level.
Therefore, the mobile station stores the order of priority of the base stations included in the announcement information received by the announcement information receiving means and notifies the control means of the reception level so that selection can be made on the base station to which a request for a message channel is to be issued. In this way, the control means is able to select the base station B to which the request should be sent.
The control means according to claim 20 includes determining means for determining whether the reception level in a reception-level determining channel is equal to or exceeds a predetermined level that enables a request for a message channel.
According to this aspect of the present invention, the control means of the mobile station can determine whether the reception level of the perch channel of, for example, the base station A or the base station B as shown in FIG. 31 is equal to or exceeds a predetermined level.
The announcing means according to claim 21 includes first arranging means for ordering the announcement information so as to arrange information relating to reception-level determining channels in a descending order of priority.
According to this aspect of the present invention, the announcing means of, for example, the base station A as shown FIG. 31 can order the announcement information such that information relating to the perch channel of the base station A and that of the base station B are arranged in the order of priority.
The announcing means according to claim 22 includes second arranging means for ordering the announcement information so as to couple information relating to each reception-level determining channel to an order of priority associated therewith.
According to this aspect of the present invention, the announcing means of, for example, the base station A as shown in FIG. 31 can order the announcement information such that information relating to the perch channel of the base station A is coupled to the priority assigned thereto and information relating to the perch channel of the base station B is coupled to the priority assigned thereto.
The transmission means according to claim 23 includes first transmission means for issuing a request for a message channel to the base station selected by the control means when a call is originated.
According to this aspect of the present invention, the control means of the mobile station as shown in FIG. 31 can select the base station B assigned the highest priority when the mobile station originates a call, so that the transmission means can request a message channel from the base station B.
The transmission means according to claim 24 includes second transmission means for issuing a request for a message channel to the base station selected by the control means when a call is incoming.
According to this aspect of the present invention, the control means of the mobile station as shown in FIG. 31 can select the base station B assigned the highest priority when the mobile station receives an incoming call, so that the transmission means can request a message channel from the base station B.
The transmission means according to claim 25 includes third transmission means for transmitting a request for a communication to the base station selected by the control means when a message channel is switched from one to another in the event of a handover of a call.
According to this aspect of the present invention, the control means of the mobile station as shown in FIG. 31 can select the base station B assigned the highest priority when a switching of channels occurs in the event of a handover, so that the transmission means can request a message channel from the base station B.
The mobile station according to claim 26 comprises control means for selecting a base station to which a request for a message channel is to be issued, based on an order of priority of a plurality of base stations included in announcement information from said plurality of base stations.
Referring to 31, based on the announcement information from the base station A including the order of priority of the base stations A and B, the mobile station can request a message channel from the base station B instead of the base station A providing a higher reception level. Thus, the base station B, provided to handle an increased local traffic, can be efficiently used to handle call originating and call incoming in the mobile station.
The mobile station according to claim 27 comprises: announcement information receiving means for receiving, from said plurality of base stations, the announcement information including the order of priority of said plurality of base stations; and transmission means for transmitting a request for a message channel to the base station selected by said control means.
According to this aspect of the present invention, the announcement information receiving means of the mobile station receives the announcement information including the order of priority of the base stations from, for example, the base station A and the base station B as shown in FIG. 31. The transmission means of the mobile station transmits a request for a message channel from a base station selected by the control means. For example, the mobile station may send the request to the base station B having the highest priority.
The mobile station according to claim 28 comprises: storage means for storing the announcement information; measuring means for measuring a reception level in reception-level determining channels in a descending order of priority of said plurality of base stations, based on the announcement information stored in said storage means and including the order of priority and based on information relating to the reception-level determining channels.
According to this aspect of the present invention, the memory means of the mobile station stores the announcement information received by the announcement information receiving means from, for example, the base station A and the base station B as shown in FIG. 31 and including the order of priority of the base stations. Measurement of the reception level by the measuring means starts with the base station B having the highest priority, based on the order of priority of the base stations A and B stored in the storing means and the information relating to the perch channel corresponding to the respective base stations. The measuring means notifies the control means of the reception level.
Therefore, the mobile station stores the order of priority of the base stations included in the announcement information received by the announcement information receiving means and notifies the control means of the reception level so that selection can be made on the base station to which a request for a message channel is to be issued. In this way, the control means is able to select the base station B to which the request should be sent.
The control means according to claim 29 includes determining means for determining whether the reception level in a reception-level determining channel is equal to or exceeds a predetermined level that enables a request for a message channel.
According to this aspect of the present invention, the control means of the mobile station can determine whether the reception level of the perch channel of, for example, the base station A or the base station B as shown in FIG. 31 is equal to or exceeds a predetermined level.
The transmission means according to claim 30 includes first transmission means for issuing a request for a message channel to the base station selected by the control means when a call is originated.
According to this aspect of the present invention, the control means of the mobile station as shown in FIG. 31 can select the base station B assigned the highest priority when the mobile station originates a call, so that the transmission means can request a message channel from the base station B.
The transmission means according to claim 31 includes second transmission means for issuing a request for a message channel to the base station selected by the control means when a call is incoming.
According to this aspect of the present invention, the control means of the mobile station as shown in FIG. 31 can select the base station B assigned the highest priority when the mobile station receives an incoming call, so that the transmission means can request a message channel from the base station B.
The transmission means according to claim 32 includes third transmission means for transmitting a request for a communication to the base station selected by the control means when a message channel is switched from one to another in the event of a handover of a call.
According to this aspect of the present invention, the control means of the mobile station as shown in FIG. 31 can select the base station B assigned the highest priority when a switching of channels occurs in the event of a handover, so that the transmission means can request a message channel from the base station B.
The base station according to claim 33 comprises: announcing means for sending announcement information including an order of priority of a plurality of base stations constituting the mobile communication system to a mobile station located in one of the radio zones.
A mobile communication system as shown in FIG. 31 is assumed. The base station A forms a relatively large service area (zone) and a base station B having a smaller transmission power than the base station A forms a relatively small service area (zone) inside the service area formed by the base station A. The mobile station is set up for a wait in the base station A. According to the invention of claim 33, the base station A can transmit the announcement information including the order of priority of the base stations. For example, the base station B could be given a higher priority over the base station A according to the announcement information.
The announcing means according to claim 34 includes first arranging means for ordering the announcement information so as to arrange information relating to reception-level determining channels in a descending order of priority.
According to this aspect of the present invention, the announcing means of, for example, the base station A as shown FIG. 31 can order the announcement information such that information relating to the perch channel of the base station A and that of the base station B are arranged in the order of priority.
The announcing means according to claim 35 includes second arranging means for ordering the announcement information so as to couple information relating to each reception-level determining channel to an order of priority associated therewith.
According to this aspect of the present invention, the announcing means of, for example, the base station A as shown in FIG. 31 can order the announcement information such that information relating to the perch channel of the base station A is coupled to the priority assigned thereto and information relating to the perch channel of the base station B is coupled to the priority assigned thereto.